You can't ignore the costs associated with transporting the furniture, sorting, inspecting, cleaning and storing the furniture. Then you need to have sales staff, finance staff, etc to help with sales. A lot of office furniture is builky, so you're looking at high transportation costs since how many desks can you fit in a box truck?
I'd guess if it's a $1,000 item new, they buy at $100 and sell for $500 with $200-300 going towards operating costs and $100 of it to profit (so 20% of the price it's sold for).
You're right, but your numbers are a bit optimistic. $1000 retail price means $500 wholesale, and no way the liquidator is going to be able sell at $500.
I buy stuff from pawn shops and thrift stores, and you can buy expensive stuff for a song.
I'd guess if it's a $1,000 item new, they buy at $100 and sell for $500 with $200-300 going towards operating costs and $100 of it to profit (so 20% of the price it's sold for).